Polymerization generally involves polymerization of one or more monomers to make a polymeric product. The polymerization reaction can be carried out using a wide variety of reactors, catalysts, and a wide variety of monomer feeds. Often, liquids, diluents or solvents are used in these polymerization reaction processes for various reasons such as to increase the efficiency of the polymerization reaction and recovery of polymer product.
An example of a polymerization process that incorporates the use of a dilutent is shown in U.S. Pat. No. 3,470,143 (Schrage et al.). Specifically, the Schrage patent discloses a laboratory scale polymerization reaction that incorporates the use of an organic fluorinated carbon compound as the dilutent.
Polymer production at commercial scale typically results in the production of a polymer product having significant amounts of entrained hydrocarbon material such as unreacted monomer, as well as various levels of liquids, solvents, diluents, catalysts and other by-products and/or non-reactive components. Separation and recovery of the polymer product from such a mixture of components typically involves passing the polymer product withdrawn from the polymerization reactor into purge bins, with nitrogen typically introduced into the purge bin to remove the undesirable materials from the polymer product. Conventionally, the nitrogen and undesirable material are vented or sent to a flare system as a waste stream.
U.S. Pat. No. 5,769,927 (Gottschlich et al.) discloses a process for treating material that is to be vented or purged from a polymer manufacturing operation using a three step separation technique. The technique includes condensation, flash evaporation and membrane separation to remove components such as ethylene, propylene and nitrogen.
U.S. Pat. No. 6,271,319 (Baker et al.) discloses a polypropylene manufacturing process that includes using a gas separation membrane to separate propylene from propane in a reactor vent stream. The separated propylene is circulated back to the polymerization reactor as feed.
EP 1 323 746 shows loading of biscyclopentadienyl catalyst onto a silica support in perfluorooctane and thereafter the prepolymerization of ethylene at room temperature.
U.S. Pat. No. 3,056,771 discloses polymerization of ethylene using TiCl4/(Et)3Al in a mixture of heptane and perfluoromethylcyclohexane, presumably at room temperature.
There are needs for improved polymerization processes, for example reducing reactor fouling at commercial scale, enhancing the commercial grade slate of polymer products produced from a given process, increasing polymer production capacity without significant investment where these process improvements necessitate more efficient recovery systems that provide environmental benefits as well as cost reductions. Therefore, depending on the various components used in polymerization processes improvements, polymer product recovery and reactor systems for recovering reusable materials and lowering emissions is needed, particularly in light of ever changing environmental constraints that continue to be imposed in the chemical manufacturing industry.